rare: Ulster. Ir. Ó Branáin. An ecclesiastical family of Fermanagh usually changed to Brennan. Ir. Mac Branáin was a sept of Roscommon. IF & SI.

Brennan:

Very numerous: widespread, especially northern half. Ir. Ó Braonáin. Woulfe cites four septs, in Kilkenny, W Meath, Galway, Kerry. The chief of these was in Ossory (Kilkenny) and many Connacht Brennans are Mac Braonáin, a different name, which also applied to an erenagh family of Fermanagh. From the personal name Braon.IF & SGG.